Transcriptomic Changes Associated with Oleate-Induced beta-Cell Proliferation in Rat Islets

Background: In nondiabetic obese individuals, β-cell mass accretion maintains glucose homeostasis by balancing levels of circulating insulin and insulin resistance. Type 2 diabetes appears when these compensatory mechanisms fail. Deciphering the pathways controlling β-cell proliferation has thus become a major research goal in the hope to identify therapeutic targets to expand β-cell mass and prevent or delay the onset of diabetes. Previously we demonstrated that fatty acids potentiate glucose induced β-cell proliferation in response to nutrient surfeit in rats. In recent studies we identified the mono-unsaturated fatty-acid oleate as a major fatty acid driving β-cell proliferation in rat islets ex vivo. Aim: To identify the transcriptional mechanisms underlying oleate-induced β-cell proliferation in rats. Method: Rat islets were exposed to 16.7mM glucose +/- oleate (0.5mM) for 48h. Proliferation was assessed by flow cytometry using c-peptide antibodies and EdU. Single cell cDNA libraries were generated using 10X Genomics technology and sequenced on the Illumina platform. Bioinformatic analyses were performed using the Cell Ranger pipeline, Seurat and Monocle. Results: Oleate induced a 3.1+/-0.4 fold increase (p<0.01; n=4) in β-cell proliferation. Following single-cell RNA sequencing, t-SNE plots revealed several β-cell sub-populations, including proliferating β-cells. Comparison between proliferative and non-proliferative β-cells identified more than 300 differentially expressed genes. Gene ontology suggested an increase in mitochondrial activity and reactive oxygen species (ROS) in proliferating β-cells. Pseudotime ordering of β cells revealed that ER-stress related genes are up-regulated prior to proliferation in response to oleate. Conclusion: Our study suggests an involvement of ROS and ER-stress in oleate-induced β-cells proliferation. Further functional analyses will substantiate the importance of these stress responses. Disclosure A. Vivoli: None. A. Castell: None. A. Pacis: None. R.M. Sladek: None. J. Ghislain: None. V. Poitout: None.